Electrosurgical methods and devices employing phase-controlled radiofrequency energy

ABSTRACT

This disclosure relates generally to electrosurgical methods and devices. In one embodiment, an electrosurgical device is provided suitable for applying phase controlled RF energy to a treatment site. The electrosurgical device comprises a multi-electrode electrosurgical probe electrically coupled to a plurality of RF generators. Also provided are methods of use of such an electrosurgical device, as well as other electrosurgical devices. The methods and devices disclosed herein find utility, for example, in the field of medicine.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority under 35 U.S.C. §119 to ProvisionalU.S. Patent Application Ser. No. 60/774,167, filed Feb. 17, 2006, andProvisional U.S. Patent Application Ser. No. 60/759,289, filed Jan. 17,2006, the disclosures of which are incorporated by reference herein.

TECHNICAL FIELD

This disclosure relates generally to electrosurgical methods anddevices. The methods and devices disclosed herein find utility, forexample, in the field of medicine.

BACKGROUND

Radiofrequency (RF) devices are used to non-specifically andnon-selectively ablate or heat different types of tissue. For example,in the field of dermatology RF devices are used to treat aging skin.Skin aging is associated with changes in the upper levels of the skinsuch as roughness of the skin due to changes in the stratum corneum andepidermis and uneven pigmentation in the epidermis. In the dermis, agingand environmental factors cause the destruction and malfunction ofcollagen and elastin fibers leading to the formation of wrinkles.Symptoms of skin aging in the epidermis are typically treated byablative methods such as chemical peels or laser resurfacing. Opticalradiation devices such as lasers are used to resurface large areas ofthe skin. While these lasers are effective in the treatment of the signsof skin aging, resurfacing the whole epidermis is often associated withside effects such as wound infections, prolonged healing times,hyperpigmentation, hypopigmentation, and scarring.

WO 05/007003 describes a method for achieving beneficial effects in atarget tissue in skin comprising treating the target tissue usingoptical radiation to create a plurality of microscopic treatment zonesin a predetermined treatment pattern. This method of resurfacing theskin, however, necessitates the use of complicated and expensive laserdevices and requires special facilities, prolonged treatment times, andhighly trained operators.

Radiofrequency (RF) devices are used to ablate localized skin lesions orto destroy the whole upper surface of the skin. However, whole skinresurfacing methods and devices cause burn like post treatment reactionsassociated with prolonged healing times, increased risk of infections,prolonged erythema, scarring, hyperpigmentation, and hypopigmentation.

U.S. Pat. No. 6,711,435 discloses a device for ablating the stratumcorneum epidermis of a subject, including a plurality of electrodes,which are applied to the subject's skin at respective points. However,this device does not ablate the epidermis and thus has no effects on thesigns of skin aging.

The RF devices described previously lack the efficacy and safety neededfor treatment of signs of skin aging in the epidermis. Some devicesresurface the whole epidermis risking multiple side effects, whileothers ablate only miniscule parts of the upper stratum corneum withouttherapeutic effects on signs of skin aging.

Symptoms of skin aging in the dermis are typically treated bynon-ablative methods, including lasers, intense pulsed light, or RFdevices that heat the dermis to trigger renewal of collagen fibers. Inorder to trigger collagen renewal, some RF devices use bipolarelectrodes to increase the heat of dermal skin layers through thecreation of electrical currents that flow parallel to the skin surface.These devices use active and return electrodes that are typicallypositioned relatively close to one another at the treatment site. Insome cases, the two electrodes are located on the same electrosurgicalprobe, and the electrodes alternate between functioning as active andreturn electrodes. Other RF devices use unipolar or monopolar electricalenergy for heating the deep layers of skin. These devices also use anactive electrode and a return electrode. The return electrode istypically positioned a relatively large distance from the activeelectrode (in comparison with bipolar devices). For both unipolar andbipolar devices, current flows along the lowest impedance path betweenelectrodes.

Other devices use a combination of optical energy and bipolar RF energyto treat the skin.

The devices described previously lack the ability to control the spatialdirections, energies, and nature of the electrical energies affectingthe treated area and thus lack the selectivity and specificity neededfor maximum efficacy in their respective therapeutic indications.Moreover, the bipolar and monopolar RF devices lack the ability to treatthe signs of aging in the epidermis. Enhanced ability to control thespatial directions and the pattern of electron flows in the treatedbiological tissue would allow effective therapy for additionaldermatological and non-dermatological disorders such as hair removal,acne, acne scars, psoriasis, bone grafting and more.

Despite advancements in the use of optical and RF devices for treatingbiological tissue, there continues to be a need in the art to developeffective electrosurgical devices and methods that are suitable fortreating a wide variety of conditions. An ideal electrosurgical methodand related devices would be capable of selectively and specificallytreating a wide variety of biological tissues and conditions effectingsuch tissues. Such a method and devices would be simple to use, andwould have minimal adverse effects.

SUMMARY OF THE DISCLOSURE

The present disclosure is directed at addressing one or more of theabovementioned drawbacks of known electrosurgical methods and devices.

In one embodiment, then, the disclosure describes a method fordelivering energy to a target site of a patient. The method comprisesplacing an electrosurgical probe into close proximity of the target siteand delivering phase controlled RF energy to the electrosurgical probe.

In another embodiment, the disclosure describes a method for modifyingliving tissue. The method comprises exposing the tissue to an electricfield, wherein the electric field is generated by an electrosurgicaldevice. The electrosurgical device comprises an electrosurgical probecomprising a plurality of electrodes electrically coupled to: (i) firstand second RF sources; or (ii) an RF source comprising first and secondRF outputs. The electrosurgical probe further comprises means forcontrolling the phase between the RF energy supplied to the plurality ofelectrodes.

In yet another embodiment, the disclosure describes an electrosurgicalsystem. The electrosurgical system comprises a means for applying RFenergy to a target site of a patient. The electrosurgical system furthercomprises a generator comprising: (i) first and second RF power sourcesor an RF power source comprising first and second RF outputs; and (ii) ameans for controlling the phase between the first and second RF powersources.

In a still further embodiment, the disclosure describes anelectrosurgical system for treating living tissue. The system isconfigured to deliver phase controlled RF electrical energy to theliving tissue.

In yet another embodiment, the disclosure describes a method fortreating living tissue. The method comprises applying an electric fieldto a surface of the tissue by means of the electrosurgical system asdescribed herein. The electrical energy causes tissue necrosis within aregion of the tissue, the width of the region being confined to asubstantially circular area of the tissue surface having a diameter inthe range of about 1 μm to about 4000 μm.

In a still further embodiment, the disclosure describes a method forcausing tissue necrosis. The method comprises contacting a surface ofthe tissue with two or more electrodes and applying an electricalpotential between the electrodes. Necrosis occurs in the area betweenthe two electrodes and is confined to a region that has a diameter inthe range of about 1 μm to about 4000 μm.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1 a and 1 b are example illustrations of the electrosurgicaldevices as disclosed herein.

FIGS. 2 a, 2 b, 2 c, and 2 d are example illustration of electrosurgicalprobes as described herein.

FIG. 3 is an example illustration of focal damage regions as formed bythe methods and devices disclosed herein.

FIG. 4 is an example illustration of focal damage regions that arelocated entirely below the surface of the tissue at the treatment site.

FIG. 5 is an example illustration of focal damage regions that begin atand extend below the surface of the treated tissue.

FIG. 6 is an example illustration of the application of phase controlledRF energy to skin surrounding a hair follicle.

FIG. 7 is an example illustration of the application of energy in theform of phased RF and light energy to skin tissue surrounding a hairfollicle.

FIG. 8 is a representation of skin tissue showing the effect ofcombining phased RF energy with optical photoselective light energy.

FIGS. 9 a, 9 b, and 9 c depict examples of electrosurgical devices asdescribed herein.

FIG. 10 is a graph showing two RF signals having different phases aswell as the signal that results from their summation.

FIG. 11 shows a circuit diagram for a typical Class D type RF generator.

FIG. 12 shows graphs of output power versus input voltage for an RFgenerator unit.

FIG. 13 is an example illustration of an electrosurgical deviceincorporating ultrasonic energy.

DETAILED DESCRIPTION OF THE INVENTION

Before describing the present invention in detail, it is to beunderstood that unless otherwise indicated, this invention is notlimited to particular electrosurgical methods, electrosurgical devices,or power sources, as such may vary. It is also to be understood that theterminology used herein is for the purpose of describing particularembodiments only, and is not intended to be limiting.

It must be noted that, as used in this specification and the appendedclaims, the singular forms “a,” “an” and “the” include plural referentsunless the context clearly dictates otherwise. Thus, for example, “apower source” refers not only to a single power source but also to acombination of two or more power sources, “an electrode” refers to acombination of electrodes as well as to a single electrode, and thelike.

Unless defined otherwise, all technical and scientific terms used hereinhave the meaning commonly understood by one of ordinary skill in the artto which the invention pertains. Although any methods and materialssimilar or equivalent to those described herein may be useful in thepractice or testing of the present invention, preferred methods andmaterials are described below. Specific terminology of particularimportance to the description in the present disclosure is definedbelow.

As used herein, the terms “may,” “optional,” “optionally,” or “mayoptionally” mean that the subsequently described circumstance may or maynot occur, so that the description includes instances where thecircumstance occurs and instances where it does not.

As used herein, the term “device” is meant to refer to any and allcomponents of a system. For example, an “electrosurgical device” refersto an electrosurgical system that may comprise components such aselectrosurgical probes, power sources, connecting cables, and othercomponents.

The terms “treating” and “treatment” as used herein refer to reductionin severity and/or frequency of symptoms, elimination of symptoms and/orunderlying cause, prevention of the occurrence of symptoms and/or theirunderlying cause (e.g., prophylactic therapy), and improvement orremediation of damage.

By “patient,” or “subject” is meant any animal for which treatment isdesirable. Patients may be mammals, and typically, as used herein, apatient is a human individual.

The terms “light” and “light energy” as used herein are meant to includevisible, infrared, and ultraviolet electromagnetic energy.

The term “phase” as used herein refers to the phase angle of analternating-current (AC) radiofrequency (RF) voltage (sometimes referredto as an “RF signal” or “RF voltage”). In some cases, the term “phase”also refers to the phase angle difference between two RF voltages.Accordingly, the term “phased RF energy” refers to RF energy thatcomprises at least two component RF voltages, wherein each component RFvoltage independently has a phase.

Disclosed herein are electrosurgical devices for applying phased RFenergy to a treatment site such as biological tissue. Typically, theelectrosurgical devices comprise an electrosurgical probe electricallycoupled to a power source, as shown in FIG. 1 a. The electrosurgicaldevice can be adapted, however, for “cordless” operation, and FIG. 1 bshows an electrosurgical device that combines an electrosurgical probewith a battery pack. The electrosurgical devices are adapted to promoteelectron conduction (i.e., electrical current) through biologicaltissue.

Without wishing to be bound by theory, it is believed that the phasecontrolled RF devices disclosed herein generate different and adjustableelectrical fields within the target site. The electrical fields arecapable of manipulating electrons within the target site, therebygenerating selective regions of elevated temperature.

The electrosurgical probes disclosed herein employ a plurality ofelectrodes disposed on a treatment surface and adapted to be applied toa target biological tissue. The electrodes may be of any appropriatesize or shape, and it will be appreciated that such will vary depending,for example, on the intended use. The treatment surface can be adaptedto treat a variety of biological tissue surfaces. Accordingly, thetreatment surface may be flat or curved. The electrodes may be uniformlydisposed across the entire treatment surface, or may be concentrated ina particular section of the treatment surface. Typically, a regularpattern will be formed by the distribution of the electrodes on thetreatment surface. The spacing between the electrode will depend, forexample, on the probe geometry and the size of the electrodes. Ingeneral, the spacing between the centers of any two adjacent electrodeswill be between about 110% and about 1000% of the diameter of theelectrodes, or, for non-circular electrodes the spacing will be betweenabout 110% and about 1000% of the maximum width of the electrodes. Fortreatment of human skin, for example, the center-to-center distancebetween adjacent electrodes may be between about 0.001 mm and about 100mm, or between about 0.01 mm and about 25 mm. In one embodiment,adjacent electrodes are spaced apart an average of about 0.01 mm toabout 0.1 mm.

One example of an arrangement of electrodes on a treatment surface isshown in FIG. 2 a. Electrodes with circular cross-section are disposedin a regular pattern over a flat treatment surface. The electrodes maybe either flush with the treatment surface, or the electrodes mayprotrude from the treatment surface.

The electrosurgical probes comprise at least 3 electrodes, and maycomprise any number of electrodes greater than 3, such as 4, 5, 6, 7, 8,9, 10, 15, 20, 50, 100, or more. For example, the probe in FIG. 2 acomprises 28 electrodes.

The electrodes are electrically coupled to a power generator capable ofproviding a plurality of power outputs. The power generator may comprisea plurality of RF sources. The power generator may also comprise asingle RF source, in which case the power generator further comprisesappropriate circuitry to split the output of the RF source into aplurality of RF signals. The power generator further comprises a meansfor controlling the phase between any two of the power outputs. Suchmeans for controlling will typically consist of phase shifting circuitryand the like, as will be appreciated by one of ordinary skill in theart.

The phase angle between at least two RF sources in the electrosurgicaldevices disclosed herein is adjustable, but it will be appreciated thatthe configuration of the electrosurgical devices may vary. In oneembodiment, the power generator comprises two RF sources and phaseshifting circuitry for adjusting the phase angle between the RF outputsof the two RF sources. In another embodiment, the power generatorcomprises first, second, and third RF sources. In one example of thisembodiment, the phases of each RF source are adjustable, such that thephase angles between the first and second, second and third, and firstand third RF sources may be independently varied. In another example ofthis embodiment, the first RF source has fixed output, and the phases ofthe second and third RF sources are adjustable. This configuration alsoallows adjustment of the phase angle between any two of the RF sources.In yet another example of this embodiment, the first and second RFsources have fixed output, and the phase of the third RF source isadjustable. This configuration allows adjustment of the phase anglebetween the first and third, and second and third RF sources. Asdescribed herein, adjustment of the phase angle between RF sources maybe accomplished automatically via a feedback loop that responds to ameasured electrical parameter (e.g., impendence at the target site,etc.), or may be accomplished manually via adjustment controls.

The electrosurgical probe may be disposable, such that it is sterilizedupon manufacture and is intended for a one-time use. Alternatively, theelectrosurgical probe may be sterilizable (e.g., autoclavable) such thatit is suitable for multiple uses and, in particular, use with multiplepatients.

In one embodiment, an electrosurgical device is provided that comprisesa means for applying light energy to the treatment site. Such means forapplying light energy include coherent sources and incoherent sources,and may include sources such as lasers, ultraviolet lamps, infraredlamps, incandescent and fluorescent lamps, light emitting diodes, andthe like. The means for applying light may be attached to theelectrosurgical probe or may be separate from the electrosurgical probe.

In another embodiment, the electrosurgical device may include a meansfor lowering the temperature of the target site. Such means includeelectrical cooling devices such as a heat sink and delivery ports fordelivering cooling liquids or gases to the target site and surroundingtissue. For example, electrical contact cooling allows cooling ofportions of the target site such as the epidermis, thereby minimizingpain and heat damage to surrounding (i.e., perilesional) skin.

Various embodiments of the electrosurgical probes disclosed herein areshown in FIGS. 2 a-2 d. FIG. 2 a shows the treatment surface ofelectrosurgical probe 1 containing no cooling devices. Twenty-eightelectrodes 2 are disposed on the treatment surface. FIG. 2 b shows thetreatment surface of electrosurgical probe 3 containing pre-coolingdevice 4. FIG. 2 c shows the treatment surface of electrosurgical probe5 containing post-cooling device 6. FIG. 2 d shows the treatment surfaceof electrosurgical probe 7 containing pre-cooling device 4 and lightemitting optical source 8.

In another embodiment, the treatment portion (e.g., head or tip) of theelectrosurgical probe of the device comprises a mechanism that allowsall or a portion of the electrosurgical probe to mechanically vibrateduring use. Such vibrations allow the treatment site to be massaged orotherwise soothed. This feature is especially preferred when the deviceis used to treat cellulite as described herein.

The electrosurgical device may comprise a means for measuring anelectrical characteristic, and optionally a feedback loop that allowsthe electrosurgical device to adjust the supplied electrical energy inresponse to the measured electrical characteristic. Such electricalcharacteristics include the electrical impedance and/or admittance ofthe target site, the current flowing between electrodes, the electricalpotential between electrodes, output voltages and phases of the RFsources, and phase differentials between RF sources. Such measurementsmay be taken in real time as the electrosurgical probe is in closeproximity to the target site, allowing the feedback loop to regulate thepower supplied by the electrosurgical device to achieve the desiredresult.

In one embodiment, the electrosurgical device is adapted for treatingthe skin. The device generates an electric field which causes a currentto flow through the stratum corneum, epidermis, and/or dermis, andcomprises a means for reducing or increasing the power dissipated in thestratum corneum in response to a variation in a measured electricalcharacteristic. Such electrical characteristics may be selected from: amagnitude of the current; a time-integration of the current; a firsttime-derivative of the current; and a second time-derivative of thecurrent. It will be appreciated that these electrical characteristicsmay be measured in biological tissues other than the stratum corneumwhen skin is not the target site.

Characteristics of the electrodes may be independently measured andmonitored by appropriate circuitry. Furthermore, the RF power sourcesmay be adapted to modify the electric field generated by the electrodesso as to reduce the current through one or more of the electrodes,substantially independently of the current through any of the otherelectrodes.

The electrosurgical devices described herein are useful in methods fordelivering energy to a target site of a patient. Target sites suitablefor the application of electrical energy using the devices disclosedherein include biological tissues such as skin, mucous membranes,organs, blood vessels, and the like. Energy is delivered to the targetsite via an electrosurgical probe, which is placed in close proximity tothe target site. By “close proximity” is meant that the probe is placedclose enough to the target site to have a desired effect (e.g., tissueablation, warming of the target site, etc.). In one embodiment, theelectrosurgical probe is placed in contact with the target site.

With the electrosurgical probe in close proximity to the target site, anRF electrical potential is applied across two or more (typically threeor four or more) electrodes present on the electrosurgical probe. Thispotential may, in some cases, cause a current to flow within the targetsite and between the electrodes. In addition or in the alternate, thepotential causes an electric field to be applied to the target site. Byemploying a plurality of RF sources and at least three electrodes,characteristics of the electric field (e.g., intensity, direction, andthe like) can be manipulated by controlling the phase angle (φ) betweenthe RF sources. The electrical field (F) generated by theelectrosurgical probe is proportional to the phase between the RFsources and other electrical parameters of each RF source. The polarityof this electrical field will vary according with the RF sources. Thesevariations will attract and consequently move free electrons, therebyheating at least a portion of the target site. In another embodiment ofthe device these free electrons will tend to flow on the more heatedpaths in the treated area, which it is established using the light,flash or laser beam, as described herein.

In one embodiment, the target site is skin, and the electrosurgicaldevice is placed in close proximity to the surface of the skin so as togenerate an electric field that causes a current to flow through thestratum corneum, epidermis, and dermis. The induced electrical currentmay flow between electrodes, but may also have a significant component(e.g., 10%, 25%, 35%, 50%, 75% or more) in the direction that isperpendicular to the skin's surface. By creating an electrical currentwithin the skin, the devices disclosed herein are able to increase thetemperature of the skin, and in some cases, ablate one or more layers ofskin. For example, the devices are useful in fully or partially ablatingthe surface of the skin. The devices are also useful in partially orfully ablating one or more layers below the surface of the skin.

In one embodiment, the electrosurgical devices may be used tonon-homogeneously increase the temperature of biological tissue asdescribed herein. In another embodiment, the electrosurgical devices maybe used to increase the temperature of biological tissue within a narrowregion relative to the size of the electrosurgical probe that isemployed.

In one embodiment, the electrosurgical devices of the disclosure may beadapted to create one or more focal damage regions at the target site.Focal damage regions are isolated regions within the target site whereintissue necrosis occurs. The sizes, locations, number, relativearrangement, and other factors of the focal damage regions aredetermined by the physical and electrical parameters of theelectrosurgical devices, as well as operating conditions of the deviceswhen in operation. Although focal damage regions may be created at anyof the target sites described herein, the remaining discussionpertaining to this embodiment will primarily use human skin as anillustrative but non-limiting example. FIG. 3 shows an illustrativeexample of a plurality of focal damage regions 9 created in skin tissue.

Without wishing to be bound by theory, it is believed that theelectrosurgical devices disclosed herein are able to create focal damageregions as a result of the adjustability of the phase angle between theRF sources. The RF sources are electrically coupled to electrodes on anelectrosurgical probe; adjustment of the phase angle between RF sourcescauses variations in the electric field that is created in the vicinityof the electrodes. Such variations include areas of intensities andareas of weaknesses in the strength of the electric field, and may beused to manipulate electrons within the target site. Thus, appropriatemodulation and adjustment of the phase between RF sources is used in thepresent disclosure to create heterogeneous electrical currents withinthe target site. Such electrical currents create regions of elevatedtemperature and are capable of creating tissue necrosis in the focaldamage regions. Therefore, the temperature of the target site isproportional to the phase of the RF sources that are connected to theelectrodes.

The dimensions of the focal damage regions may be varied as desired andas appropriate for the intended application. For example, in treatinghuman skin, the focal damage regions may be substantially columnar andperpendicular to the surface of the skin being treated. The columns maybegin at or below the surface of the skin and extend to some depth belowthe surface. Therefore, the columns have proximal ends and distal ends,wherein the proximal end is either at the surface of the skin or nearestthe surface of the skin, and the distal end is furthest from the surfaceof the skin. When not at the surface of the skin, the proximal ends ofthe columns may be located about 0.1, 1, 2, 3, 4, 5, 10, 25, or 50 μmbelow the surface of the skin. The distal ends of the columns may belocated about 1, 5, 10, 25, 50, 100, 1000, 2000, or 4000 μm below thesurface of the skin. The width (i.e., diameter) of the columns may alsovary, and may be between about 1 μm and about 7000 μm, or between about10 μm and about 4000 μm. For example, the columns may be at least 1, 10,20, 30, 40, 50, 100, 150, 200, 250, 500, 800, 1000, 2000, or 5000 μm inwidth. In one embodiment, the focal damage regions have widths that arein the range of about 50-100 μm, or about 50-70 μm. Tissue damage withinthe focal damage regions may be isolated within the upper layers of skinsuch as within the stratum corneum, or may be limited to skin cellslocated below the stratum corneum. Tissue damage may also extend acrossa plurality of layers of skin. Focal damage regions created by theelectrosurgical devices disclosed herein may therefore extend throughthe stratum corneum and into the underlying layers of the epidermis anddermis. Focal damage regions may also be limited to the layers of theepidermis and dermis that are below the stratum corneum. Focal damageregions may be confined to the stratum corneum. Focal damage regions mayalso be confined to the stratum corneum and epidermis. Focal damageregions may also be confined to the stratum corneum, epidermis, anddermis. In general, the depth of the focal damage region may be selectedby the operator of the device.

It will be appreciated that the focal damage regions may have shapesother than columnar, such other shapes including pyramidal, egg-shaped,or spherical. Furthermore, the cross-section of the focal damage regions(i.e., a cross-section taken parallel to the surface of the skin) mayhave any shape, including regular shapes such as circular, square, oval,triangular, polygonal, as well as irregular shapes.

Limitation of tissue necrosis to within the focal damage regions allowsclose control of the total area of tissue that is damaged. By adjustingthe density and physical dimensions of the focal damage regions (whichis accomplished by adjusting the phase relationship between electrodes,the RF power delivered to the electrodes, and other factors as describedherein), the amount of damaged skin can be controlled. For example,using the methods disclosed herein, at least about 1%, 5%, 10%, 15%,20%, 25%, 50%, or 75% of the tissue in the treated region is damaged.

Another characteristic of the focal damage regions is density—i.e., thenumber of focal damage regions that are created per unit area of tissueat the target site. Typical densities are at least about 10, 100, 200,500, 1000, 2000, or 3000 cm⁻². In one embodiment, the density of focaldamage regions is within the range of about 100-3000 cm⁻². Since thefocal damage regions may be located entirely below the surface of thetissue at the target site, the density of focal damage regions can alsorefer to the number of regions in a unit area of a slice of the tissueat the target site. Most conveniently, such a slice of tissue will beparallel to the surface of the tissue at the target site. Again, withoutwishing to be bound by theory, the density of focal damage regions is afunction of the number and density of electrodes, the phase relationshipof the RF energy applied to the electrodes, operating conditions, andother factors that will appreciated by the skilled artisan.

Furthermore, the focal damage regions can be created in a pattern in thetarget region. As with focal damage region density, the orientation offocal damage regions at the target site is a function of the number anddensity of electrodes, the phase relationship of the RF energy appliedto the electrodes, operating conditions, and other factors that willappreciated by the skilled artisan.

The amount of energy required to create each focal damage region willvary with operating conditions, type of biological tissue, size of thedamage region, and other factors. In one example, the amount of energydelivered to create each damage region is about 1 mJ*cm⁻³.

It will be appreciated that the physical dimensions, density, totalnumber, and distribution pattern of the focal damage regions may varydepending on the intended application. The number and arrangement ofelectrodes, the phase of the RF energy applied to the electrodes, andother factors are selected based on the desired therapeutic effect.

FIG. 4 shows a graphical representation of focal damage regions havingproximal ends located below the surface of the tissue being treated bytreatment probe 10. The region of tissue 11 between the proximal ends offocal damage regions 12 and the surface of the tissue is maintained at acooler temperature compared with the tissue in the focal damage regions.Regions of tissue 13, located between focal damage regions 12, are alsocooler than the tissue within the focal damage regions. FIG. 5 shows agraphical representation of focal damage regions 12 that extend downward(i.e., deeper into the tissue) from the surface of the tissue.

The electrosurgical probe may be translated (i.e., moved) parallel tothe skin surface during the application of electrical energy to theskin. Such translation may occur with the probe either in contact withthe skin or in close proximity to the skin. Translation of the probeallows for enlarged areas of treatment, improved heat dissipation, andother benefits as will be appreciated by the skilled artisan. The RFsources can also be programmed and controlled, using standard controlcircuitry, to apply RF energy to the electrodes in a time-dependentfashion, such that specific patterns of focal damage regions are createdbased on the rate and direction of translation of the electrosurgicalprobe.

For the treatment of lesions, scars, regions of pigmentation, etc., thepattern of focal damage regions can be predetermined using, for example,an image of the lesion acquired by digital imaging techniques andtransferred to a control unit integrated with the electrosurgicaldevice. For example, in a method for treating acne on a patient, theacne can be photographed and the electrosurgical device appropriatelypreprogrammed to ablate only lesions with specific lesions or pimples.Other examples include creating focal damage regions only on or nearpsoriatic lesions, or only in the region of a skin tattoo. In anotherexample, the device is used to treat a patient with melasma havinghyper-pigmented areas on part of the face. The electrosurgical devicemay be programmed to ablate the whole face with low depths of ablation.Alternatively, areas of the face characterized by greaterhyper-pigmentation may be treated with a higher density of focal damageregions while areas of the face that are characterized by lesshyperpigmentation may be treated with a lower density of ablatedregions.

The tissue within the focal damage regions may be wholly or in partablated or damaged. Regions of tissue between the focal damage regionswill typically be heated due to dissipating heat from the electrodes,although such regions will not typically be ablated or permanentlydamaged.

In some embodiments, treatment of conditions of the skin using focaldamage regions as described herein has the advantage of minimizinghealing times due to minimized damage to the tissue surrounding thefocal damage regions.

In addition or as an alternative to creating focal damage regions,electrical energy applied via the electrosurgical devices disclosedherein may be used to heat, but not destroy and/or damage, the targetsite. For example, when the target site is skin, heat may be applied toeffect collagen remodeling in a method for treating wrinkles.

Phase controlled RF devices and methods as disclosed herein may becombined with other sources of energy. In some embodiments, the use ofadditional forms of energy allow synergistic effects for treatment ofconditions such as skin disorders, skin aging and hair removal. Forexample, focused ultrasound energy may cause micro-vibrations insusceptible living tissue. The micro-vibrations caused by the ultrasounddiffer for different types of tissue (e.g., skin; keratinocytes orepidermal cells, hard keratin such as the shaft of hairs, etc.). Sincefocused ultrasound energy can differentiate physical properties ofliving tissue (e.g., treated from untreated tissue duringelectrosurgical procedures, adipose subdermal cells from connectivetissue cells, etc.), it can amplify the selectivity of the effects ofphase controlled RF energy. In one embodiment of the methods and devicesdisclosed herein, phase controlled RF and ultrasound energy are used totreat tissue. Examples of uses for the combination of phase controlledRF and ultrasound energy include the removal of hair and therapy ofcellulite hair (e.g., hair removal or therapy that is safer and moreefficient than existing methods).

The methods disclosed herein may further comprise a pretreatment stepsuch as: treatment with a topical anesthetic; cooling; and treatmentwith light energy. Topical anesthetics such as lidocaine and the likemay be applied as needed, such as 30-60 minutes prior to treatment withthe electrosurgical device. Cooling of the target site as a pretreatmentstep may involve application of cooling agents such as gels, liquids, orgases. Examples include water and saline solutions, liquid nitrogen,carbon dioxide, air, and the like. Cooling may also involve electricalcontact cooling. Typically, cooling of the target site is accomplishedjust prior to treatment with the electrosurgical probe, and has theeffect of reducing pain and unwanted heat damage to the tissuesurrounding the target site. Pretreatment with light energy may beaccomplished using a light source integrated with the electrosurgicalprobe or with a separate light source, as described herein. Light energyis capable of effecting photothermolysis, and is useful in selectivelyheating regions of the target area. Accordingly, light energy can beused in conjunction with the electrosurgical devices. For example,regions of darker coloration such as hair and skin characterized by thepresence of relatively large amounts of melanin (e.g., moles,hyperpigmented lesions, and the like) may be selectively heated, as suchareas will absorb more light energy compared with regions with lesspigmentation. Light energy may also be used to create preferredconduction pathways for the electrical currents that are produced by theelectrosurgical probes described herein. Methods of treatment usinglight energy as well as the electrosurgical devices disclosed herein areparticularly suitable for the treatment of hyperpigmented lesions,melasma, lentigines, wrinkles, and acne scars, as well as in hairremoval, and the clearing of vascular lesions.

After treatment of the target site with the electrosurgical devicesdescribed herein, certain post-treatment steps may also be taken. Suchpost-treatment steps include treatment with a topical anesthetic asdescribed above, and cooling of the target site and surrounding tissueas described above.

The electrosurgical methods and devices disclosed herein may also beused in conjunction with an additional means for applying energy such aslight and/or ultrasound energy to the target site. For example, theelectrosurgical probe may comprise an optical light source (e.g.,lasers, incandescent lamps, gas-discharge lamps, and the like), ahigh-frequency ultrasound source, an infrared light source, anultraviolet light source, or any combination thereof. Such additionalmeans for applying energy may be electrically coupled to the same powersource(s) that provide power to the electrodes of the electrosurgicalprobe, or may be electrically coupled to a separate power source.

The methods and devices disclosed herein are useful in the field ofelectrosurgery in general, and more specifically in procedures that aresuitable for treatment using RF energy. For example, the methods anddevices disclosed herein may be employed in procedures useful in thetreatment of medical and aesthetic disorders and conditions affecting apatient's skin and subcutaneous tissue, including the following: skinresurfacing procedures; lessening the appearance of or removal ofpigmentations; lessening the appearance, removing, or otherwise treatingcellulite; therapy or removal of wrinkles, vascular lesions, scars andtattoos; hair removal and hair transplant procedures; treatment of skincancer; skin rejuvenation; treatment of acne and psoriasis; debridementof chronic skin ulcers; and blepharoplasty procedures.

The methods and devices disclosed herein are also useful in treating thesigns of skin aging, including treatment of skin roughness, unevenpigmentation, wrinkles, and dilated capillaries.

Other applications for the devices and methods disclosed herein, and inparticular the creation of focal damage regions in the target site,include removal of aging or diseased skin, thereby allowing fastregeneration by the non-ablated skin of the surrounding areas.

Many of the conditions and methods of treatment mentioned above make useof the devices of the disclosure and their ability to selectively heattissue below the surface of the tissue being treated. For example, thedevices disclosed herein are useful in methods for treating wrinkles andother signs of aging. Warming the collagen below the surface of the skincauses the collagen molecules to reorient on a molecular level, therebyeliminating or reducing the presence of wrinkles. The use ofphase-controlled RF allows selective heating of regions of collagenwithout causing heating or damage of surrounding areas.

In another example, the devices disclosed herein are useful in methodsfor removing hair and for methods of hair transplantation. Thephase-controlled RF can be used to create electric fields thatspecifically and selectively heat hair and hair follicles, particularlywhen such hair and hair follicles are located between electrodes such asis shown in FIG. 6. Furthermore, treatment of hair (in addition to othermethods of use) can benefit by the use of light energy in addition tothe electrosurgical probe, as disclosed herein and shown in FIG. 7. FIG.8 further shows the effects of combining light energy with phased RFenergy in treating skin and hair or hair follicles therein. In FIG. 8,heat from the light source accumulates in the melanin rich hair and hairfollicle (Region 1), supplementing heat from RF energy. This enhancesselectivity, thereby allowing selective warming and/or damage to hairswith decreased warming and/or damage to the surrounding, relativelymelanin poor areas (Region 2).

All patents, patent applications, and publications mentioned herein arehereby incorporated by reference in their entireties. However, where apatent, patent application, or publication containing expressdefinitions is incorporated by reference, those express definitionsshould be understood to apply to the incorporated patent, patentapplication, or publication in which they are found, and not to theremainder of the text of this application, in particular the claims ofthis application.

It is to be understood that while the invention has been described inconjunction with the preferred specific embodiments thereof, that theforegoing description as well as the examples that follow, are intendedto illustrate and not limit the scope of the invention. It will beunderstood by those skilled in the art that various changes may be madeand equivalents may be substituted without departing from the scope ofthe invention, and further that other aspects, advantages andmodifications will be apparent to those skilled in the art to which theinvention pertains.

EXAMPLES Example 1 Example Configurations of Electrosurgical Device

Three example configurations of phase controlled RF devices are shown inFIGS. 9 a, 9 b, and 9 c. In FIG. 9 a, a phase controlled RF (PCRF)device with only four electrodes is shown. The electrodes are connectedas two pairs, labeled RF1 and RF2. Voltages V1 and V2 are applied to RF1and RF2, respectively, using two independent RF generators. Examples ofV1 and V2 are shown in FIG. 10. The voltage relation between V1 and V2is described by equation (1).V1=V2+φ  (1)Allowing equations (2)-(5) to be assumed as follows,V1=V ₀ sin(2πft+θ)  (2)V2=V′ ₀ sin(2πft+Ψ)  (3)V ₀ =V′ ₀  (4)φ=θ−Ψ  (5)then V₀₁ can be expressed as in equation (6)V ₀₁=2×V sin(2πft+θ)sin(2πft).  (6)V₀₁ is the equivalent internal potential that is used to manipulateelectrons within the target site. The phase between the RF generators iscontrolled by the RF Phase Control Unit, also shown in FIG. 9 a. Each RFgenerator is capable of delivering, for example, up to 500 watts to atypical load of 50 ohms at a frequency of 1 MHz, although it will beappreciated that such values may be greater or lesser as appropriate.Each RF generator has different inputs to control: (1) the power out ofthe unit; (2) the phase of the RF signal; (3) pulse duration; and (4)ON/OFF function. The device shown in FIG. 9 a may be implemented in avariety of ways, and it will be appreciated that the efficiency of theunit (i.e., Output Power as a ratio to Input Power) will varyaccordingly. A Class D type RF generator is used, in one example, toprovide a device with high efficiency (˜90%). FIG. 11 shows a typicalClass D type RF generator.

The RF Phase Control Unit is a low power unit that sets the phase ofeach RF generator unit. This unit implements a simple square wavegenerator where the phase of this square wave is set by aresistor-capacitor (RC) circuit or in a digital manner by setting theappropriate register of the square wave generator chip. Examples of thiskind of semiconductor chip are chips named by the number 555 or 556(dual 555) or any common phase-locked loop (PLL) chips. Another functionof the RF Phase Control Unit is to control the power out of the RFgenerator units (RFGUs), which is done by controlling the input voltagesupplied to the RFGUs. The output power of an RFGU is proportional tothe input voltage (see FIG. 12). The input voltage is set on the ACpower supply unit.

In the device shown in FIG. 9 a, the voltage supplied by the AC powersupply unit is controlled by the microcontroller unit. In addition,functions such as ON/OFF, pulse duration, etc, are define on themicrocontroller unit and transmitted to the Phase Control Unit (PCU),which in turn controls the RFGUs.

The device in FIG. 9 a also includes an Electrical Cooler Unit (ECU). Inone embodiment, this unit is a controlled power supply that generates aDC current to drive one or more electro-thermal TEK cooling device(s).For a cooling device that is capable of generating a 30° C. deltabetween the two sides of the device, for example, the electrodes couldbe maintained at 5° C. with an ambient temperature of 35° C. This may beaccomplished by maintaining one side of the TEK at ambient temperatureusing, for example, the Fan unit shown in FIG. 9 a, which suppliesambient air flow to the electrodes. The input power to the Fan unit issupplied by the AC power supply unit. The AC power supply unit maysupply, for example, a voltage that is proportional to the temperatureof the electrodes. This allows noise and power to be optimized such thata desired temperature is achieved at the target tissue. It will beappreciated that alternative methods of cooling (including various heatsinks liquid cooling methods, and the like) may be used in the devicesdisclosed herein.

The AC power supply unit may supply all the needed voltages and currentsfor the various components of the device. The input voltage range forthe AC power supply unit is preferably within the standard range, i.e.,AC 95V-230V. The output voltages and currents will vary according to theneeds of the components, and may include: +3.3V at 5 A, +12V at 2 A, and+0V to 60V at 8 A, with such voltages and currents being supplied toeach component and/or each of multiple RF generators.

The control interface unit allows control of the device by the user,such as a medical practitioner (for devices intended for hospital use)or an individual (for devices intended for personal use such as hairremoval devices) and may include a computer interface, digital controlsand displays, analog dials and controls, and the like. Such controlsinclude, for example, power ON/OFF, control of menu setting, emergencypower OFF push button, Power inlet, etc.

In FIG. 9 b, another PCRF device is shown. This device is similar to thedevice shown in FIG. 9 a, except that a single RF generator is used, theoutput of which is supplied to multiple phase shift modules to generatedifferent electrical phases at the electrodes. In instances where arelatively large number of different phases are desired or required, theapproach exemplified by the device in FIG. 9 b may be relatively moreeconomical as compared with the approach exemplified by the device inFIG. 9 a.

In FIG. 9 c, another PCRF device (particularly suitable for cases inwhich low power is needed) is shown. A semiconductor chip with a custompackage of VFBGA (very fine pitch ball grid array) type circuitry can beused to control the electrodes, RF generator, RF phase control unit,microcontroller unit, fan control unit and control interface unit. Thesystem comprises a power supply unit, the custom semiconductor chip andrelatively few buttons on a control unit for human interface. In theexample shown, the control unit and power unit electrically attach tothe semiconductor chip via a minimal number of wires, as appropriate.

Example 2 Example Configurations of Electrosurgical Device

An example configuration of a phase controlled RF device is shown inFIG. 13. A focused ultrasound emitter is coupled with 2 pairs ofelectrodes (2 on each side, in the example shown) that are supplied withphase controlled RF energy. During treatment of living tissue (e.g.,hair removal) both phased RF and ultrasound energies are emittedsimultaneously. The applied energy and physical properties of the targettissue cause overheating of the hair shaft and a bulge to form incomparison to surrounding skin. This allows a selective pigment and/orhair removal system.

Example 3 Treatment of Hair Model Using Phased RF Energy

Nylon fishing thread was used as a simulator (i.e., model) for hair. Thenylon thread is similar to hair in that it has similar diameter, doesnot absorb water, and is non-conductive. Other simulators that weretried are cotton thread and a metallic needle.

The tissue model used was chicken breast. When implanted in the model,nylon thread maintains the electrical property of being non-conductive.An infrared camera allowing a resolution of 100 μm was used to takereal-time images of the model.

An electrosurgical probe comprising 4 electrodes was used inphase-controlled mode. The results were compared with results obtainedfrom the same electrosurgical probe operating in a regular 2-electrodebipolar mode (i.e., only 2 electrodes were powered and the RF energy wasnot phase-controlled). In the regular bipolar 2-electrode setting, theelectrosurgical device did not show selective heating of the hair model.The nylon thread remained cooler than the surrounding tissue. In thephase-controlled mode, the electrosurgical device showed selectiveheating of the hair model. The temperature of the nylon thread was foundto be 20-40° C. warmer than the surrounding tissue.

1. An electrosurgical system comprising: an electrosurgical probe forapplying at least a heat treatment to tissue of a patient below thesurface of the skin, the probe being configured to contact the surfaceof the skin and comprising at least one substantially straight row ofelectrodes, the at least one row of electrodes including at least afirst electrode, a second electrode, and a third electrode; and agenerator comprising a plurality of RF outputs and phase shiftingcircuitry for controlling the phase therebetween, wherein connectionbetween the RF outputs and the electrodes is configured such that atleast two electrode pairings are formed, the at least two electrodepairings including a first pair comprising the first and secondelectrodes, and the second pair comprising the first and thirdelectrodes, wherein the phase shifting circuitry is configured such thatthe RF outputs apply a respective RF electrical potential across eachpairing at different phase, and wherein the phase differential betweenpairings results in electrical currents being established between atleast one of the pairings at an angle to the surface of the skin causingheating of the tissue below the surface of the skin.
 2. The Systemaccording to claim 1, wherein the angle is substantially perpendicular.3. The electrosurgical system of claim 1, wherein the electrodes incross section are substantially rectangular, and wherein the electrodesare disposed on the treatment surface such that there is at leastbetween about 0.01 mm and about 25 mm between the centers of any twoelectrodes.
 4. The electrosurgical system of claim 1, wherein the RFenergy causes elevation of the temperature within columns of the tissue,the columns of tissue being substantially perpendicular to a surface ofthe tissue.
 5. The electrosurgical system of claim 1, further comprisinga means for adjusting the electrical currents in the living tissue inresponse to a measured characteristic of the current in the livingtissue.
 6. The electrosurgical system of claim 5, wherein the measuredcharacteristic is selected from the magnitude, time-integration, firstderivative with respect to time, and second derivative with respect totime.
 7. An electrosurgical system comprising: an electrosurgical probefor applying at least a heat treatment to tissue of a patient below thesurface of the skin, the probe being configured to contact the surfaceof the skin and comprise at least one substantially straight row ofelectrodes, the at least one row of electrodes including a first pair ofelectrodes and a second pair of electrodes, wherein the second pair ofelectrodes is arranged along the row to sandwich the first pair ofelectrodes; and a generator comprising at least first and second RFoutputs and phase shifting circuitry; wherein each RF output providespower to a respective pair of the first and second pair of electrodes,the phase shifting circuitry being configured for effecting a phasedifferential between the first and second RF outputs such thatelectrical currents are established between at least the second pair ofelectrodes which are at an angle to the surface of the skin, and whereinthe electrical currents result in heating of the tissue below thesurface of the skin for treatment thereof.
 8. The System according toclaim 7, wherein the angle is substantially perpendicular.
 9. Theelectrosurgical system of claim 7, wherein the electrodes in crosssection are substantially rectangular, and wherein the electrodes aredisposed on the treatment surface such that there is at least betweenabout 0.01 mm and about 25 mm between the centers of any two electrodes.10. The electrosurgical system of claim 7, wherein the RF energy causeselevation of the temperature within columns of the tissue, the columnsof tissue being substantially perpendicular to a surface of the tissue.11. The electrosurgical system of claim 7, further comprising a meansfor adjusting the electrical currents in the living tissue in responseto a measured characteristic of the current in the living tissue. 12.The electrosurgical system of claim 11, wherein the measuredcharacteristic is selected from the magnitude, time-integration, firstderivative with respect to time, and second derivative with respect totime.